This invention relates to the field of nonwoven fabrics or webs and their manufacture. More particularly, it relates to such nonwoven fabrics which are comprised of at least one layer of staple fibers or filaments or continuous filaments. One example of such nonwoven fabric is a fabric wherein the fibers are microfibers having an average diameter of about 10 microns. Such fibers are commonly comprised of a thermoplastic such as polyolefins such as polypropylene, polyamides, polyesters and polyethers and these microfibrous fabrics or webs have a great ability to absorb liquid materials such as oils. The webs may also be made hydrophilic through various treatments and may be used to absorb aqueous solutions.
Uses for such absorbent microfibrous webs are in such applications as oil and chemical spill cleanup materials, industrial wipers, food service wipes, diapers, feminine hygiene products and barrier products such as medical gowns and surgical drapes.
Various steps have been undertaken to treat the microfibrous webs in order to improve conformability, bulk and especially softness. While some of the techniques currently in use achieve some degree of success, all have certain drawbacks.
The technique of mechanical softening the nonwoven web in a method such as washing is a time consuming, batch process which does not lend itself to the requirements of industrial production. In addition, large volumes of water from the washing process must be handled, either by recycling or disposal and the web must be dried. Drying a nonwoven web is an energy consuming process which is somewhat difficult to control in a commercial setting, sometimes resulting in remelted, glazed or otherwise damaged webs.
The technique of mechanical softening by stretching does not provide the degree of softness being sought for some applications. The technique of chemical softening by treating a web with surface active chemicals also does not provide the degree of softness being sought for some applications.
Accordingly, it is an object of this invention to provide a microfibrous web which is softer than either chemical or mechanical softening alone and which can be performed in a continuous industrial production operation.